- 2 lb small (1- to 1 1/2-inch) potatoes, preferably new potatoes
- 1 1/2 teaspoons salt
- 3 tablespoons finely chopped shallots (about 2)
- 1/2 tablespoon Dijon mustard
- 1 tablespoon whole-grain mustard
- 1 tablespoon white-wine vinegar, or to taste
- 1/2 teaspoon black pepper
- 3 tablespoons olive oil
- 2 tablespoons chopped fresh flat-leaf parsley
- Cover potatoes with water by 1 inch in a 3- to 4-quart saucepan, then bring to a boil with 1 teaspoon salt. Simmer, partially covered, until potatoes are tender, about 10 minutes, then drain.
- Whisk together shallot, mustards, vinegar, pepper, and remaining 1/2 teaspoon salt in a large bowl, then add oil in a slow stream, whisking until emulsified.
- When potatoes are just cool enough to handle, halve them, then add to vinaigrette along with parsley and toss to combine. Serve warm or at room temperature.